煤系硫铁矿浮选尾矿热化学活化脱硅制备铝精矿

Desilication of coal-derived pyrite flotation tailing for preparing alumina concentrate by thermochemical activation process

提出热活化脱硅技术处理某煤系硫铁矿浮选尾矿制备铝精矿,对制备氧化铝精矿的工艺制度及脱硅机理进行研究。结果表明:该尾矿适宜的热化学活化脱硅制度为活化焙烧温度1 150℃、焙烧时间15～20 min、碱浸溶硅温度125～140℃、溶出时间30 min、NaOH浓度140 g/L。在此条件下,对Al2O3和SiO2含量分别为46.22%和28.33%(质量分数)的硫铁矿浮选尾矿,焙砂SiO2溶出率达到71.91%,所得铝精矿中Al2O3含量达69.29%,铝硅比5.59。XRD结果表明:硫铁矿尾矿中伊利蒙脱石、高岭石和叶腊石等铝硅酸矿物在焙烧过程中活化分解生成无定形SiO2和少量莫来石,与此同时,一水硬铝石转变成α-Al2O3。在焙砂的碱浸过程中,无定形SiO2溶解于NaOH溶液被脱除,而α-Al2O3和莫来石不能溶解,同时生成的水合铝硅酸钠(Na8Al6Si6O24(OH)2(H2O)2)将导致SiO2溶出率降低。焙烧过程中尾矿中的黄铁矿转化为赤铁矿、锐钛矿部分转化成金红石,在碱浸过程中它们均不会溶解而进入铝精矿中。

Aiming at preparing alumina concentrate from coal-derived pyrite flotation tailing,a desilication technique using thermochemical activation process followed by alkali leaching was proposed,and the suitable processing parameters and desilication mechanism were investigated. The results show that the optimal thermochemical activation processing parameters are as follows： roasting temperature 1 150 ℃,roasting time 15 20 min,alkali leaching temperature 125 140 ℃,leaching time 30 min and NaOH concentration 140 g/L. In this case,an alumina concentrate with 69.29%Al2O3 and mass ratio of alumina to silica（A/S） of 5.59 is obtained from a pyrite flotation tailing bearing 46.22%Al2O3 and 28.33%SiO2（mass fraction）,and the corresponding desilication ratio is 71.91%. XRD results show that aluminosilicates of the pyrite flotation tailing,including illite-montmorillonite,kaolinite and pyrophyllite,are decomposed into amorphous SiO2 and small amount of mullite after thermochemical activation. Meanwhile,diaspore is transformed into α-Al2O3. During the alkali leaching of activated materials,amorphous SiO2 dissolves in the caustic soda,while mullite and α-Al2O3 do not dissolve,and the formation of sodium aluminosilicate hydrate（Na8Al6Si6O24（OH）2（H2O）2） during leaching leads to a decrease of desilication. Otherwise,rutile from thermal transformation of portion anatase,as well as hematite from oxidation,is not capable of being dissolved in alkali solution and shifted to alumina concentrate.